Advanced Materials Research Vols. 732-733

Abstract: A method of autoregressive (AR) based on discrete Fourier analysis is proposed to forecast the indexes of unbalance factor and total harmonic distortion. The discrete Fourier transform of the index sequence is analyzed and the low frequency components are extracted. Autoregressive method is applied to forecast each low frequency component. Through inverse discrete Fourier transform, the forecasting low frequency components are inverted to forecasting sequence of the index in time domain. Actual data is used to test this method and the results show that discrete Fourier analysis is possible to reduce the influence of high frequency noise and that the AR method based on Fourier transform can effectively forecast the indexes of unbalance factor and total harmonic distortion.

Abstract: Due to the uncertain price and stochastic load, power supply companies will face the trade-off between profits and risks when exercising Interruptible Load Management (ILM). Customers of different type are looked as sub-markets with different risk and benefit. A model is established for Interruptible Load (IL) in the framework of portfolio theory, with the object of maximizing the expected profits and risks of conditional value at risk (CVaR). Genetic Algorithm (GA), is adopted to solve the model. Finally, a numerical example is served for demonstrating the market property of high profits accompanied by high risks and the feasibility of the proposed model, thus a reference is provided to a power supply company to manage risks.

Abstract: Parallel harmonic resonance is closely related to the singularity of a node admittance matrix. It was found that the smallest eigenvalue of the matrix defines the mode of parallel harmonic resonance. This paper applies eigenvalue theory and modal sensitivity analysis method to determine which network components contribute significantly to a harmonic resonance phenomenon. Case study results further confirm the theoretical correctness and effectiveness. Thus, this practical method not only provides significant measures for harmonic resonance manage, but also support theoretical and experimental bases for the component parameter design.

Abstract: It is an urgent problem to solve for generation companies that how to find the optimal bidding strategy to obtain the highest profits and to decrease the risk to the lowest level. This paper presented a new bidding decision model with risk management for generation companies based on the conditional value at risk (CVaR). In the process of building the optimal bidding decision models, three situations are considered separately, including only consider maximize the expected return or the CVaR value of benefit, and considering the benefit and risk (CVaR). By this method, the generation companies can be determined the two decision variables of bidding price and bidding output to maximize its revenue at the same time to declare the risk.

Abstract: To improve the power quality and efficiency on feeding unbalanced loads, this paper proposes a scheme of instantaneous current compensation that can modify the power factor and balance the three-phase currents simultaneously. The method of instantaneous space vectors can compensate the reactive power effectively, but the problems of unbalanced load currents remains. This paper suggests a method that can mitigate the unbalanced load currents by setting the active power as a constant for each cycle. Field measurement data were analyzed. Simulation results confirmed the feasibility of correcting the power factor and balancing load currents simultaneously using the proposed method.